arc: Avoid the resize operation in GetImageForScale() whenever possible

arc: Avoid the resize operation in GetImageForScale() whenever possible

to remove UI jank.

ArcAppIcon::Source::GetImageForScale() is one of the lowest level
functions for the ARC app icon stuff which can easily be called
thousands of times while e.g. the user enters a few characters to
the app search box.

However, the function does a relatively heavy Skia operation,
gfx::ImageSkiaOperations::CreateResizedImage() with RESIZE_BEST,
against either IDR_APP_DEFAULT_ICON or IDR_ARC_SUPPORT_ICON_NN,
and b/33377533 shows that the operation actually slows down Chrome
OS UI significantly.

For example, on a recent Chromebook, pressing Search, then entering
pressing characters to the app search box freezes the browser's UI
thread for about (5 * num_of_arc_apps * num_of_key_presses)
milliseconds. If you enter 5 characters, and your device has 50 ARC
apps, the UI freezes for about 1.25 seconds.

This CL removes the bottleneck by avoiding the heavy resize operation
when possible.

BUG=673571
TEST=Install 50+ ARC apps to make the issue much more apparent, press
 Search to show the text area for app search, enter a few characters
 to the area, confirm that the UI is still responsive.
TEST=chrome://tracing (input latency mode) does not show any long
 tasks in the UI thread anymore.

Review-Url: https://codereview.chromium.org/2567253002
Cr-Commit-Position: refs/heads/master@{#438238}
(cherry picked from commit e3f59ed9bdc15fc1cccc737e425d40a077c36a32)

Committed: https://chromium.googlesource.com/chromium/src/+/67fac5e016806049e25da6d6e0dd06be69170bb1

[Yusuke Sato, 2016-12-15 16:14:22]

Description was changed from

==========
arc: Avoid the resize operation in GetImageForScale() whenever possible

to remove UI jank.

ArcAppIcon::Source::GetImageForScale() is one of the lowest level
functions for the ARC app icon stuff which can easily be called
thousands of times while e.g. the user enters a few characters to
the app search box.

However, the function does a relatively heavy Skia operation,
gfx::ImageSkiaOperations::CreateResizedImage() with RESIZE_BEST,
against either IDR_APP_DEFAULT_ICON or IDR_ARC_SUPPORT_ICON_NN,
and b/33377533 shows that the operation actually slows down Chrome
OS UI significantly.

For example, on a recent Chromebook, pressing Search, then entering
pressing characters to the app search box freezes the browser's UI
thread for about (5 * num_of_arc_apps * num_of_key_presses)
milliseconds. If you enter 5 characters, and your device has 50 ARC
apps, the UI freezes for about 1.25 seconds.

This CL removes the bottleneck by avoiding the heavy resize operation
when possible.

BUG=673571
TEST=Install 50+ ARC apps to make the issue much more apparent, press
 Search to show the text area for app search, enter a few characters
 to the area, confirm that the UI is still responsive.
TEST=chrome://tracing (input latency mode) does not show any long
 tasks in the UI thread anymore.

Review-Url: https://codereview.chromium.org/2567253002
Cr-Commit-Position: refs/heads/master@{#438238}
(cherry picked from commit e3f59ed9bdc15fc1cccc737e425d40a077c36a32)
==========

to

==========
arc: Avoid the resize operation in GetImageForScale() whenever possible

to remove UI jank.

ArcAppIcon::Source::GetImageForScale() is one of the lowest level
functions for the ARC app icon stuff which can easily be called
thousands of times while e.g. the user enters a few characters to
the app search box.

However, the function does a relatively heavy Skia operation,
gfx::ImageSkiaOperations::CreateResizedImage() with RESIZE_BEST,
against either IDR_APP_DEFAULT_ICON or IDR_ARC_SUPPORT_ICON_NN,
and b/33377533 shows that the operation actually slows down Chrome
OS UI significantly.

For example, on a recent Chromebook, pressing Search, then entering
pressing characters to the app search box freezes the browser's UI
thread for about (5 * num_of_arc_apps * num_of_key_presses)
milliseconds. If you enter 5 characters, and your device has 50 ARC
apps, the UI freezes for about 1.25 seconds.

This CL removes the bottleneck by avoiding the heavy resize operation
when possible.

BUG=673571
TEST=Install 50+ ARC apps to make the issue much more apparent, press
 Search to show the text area for app search, enter a few characters
 to the area, confirm that the UI is still responsive.
TEST=chrome://tracing (input latency mode) does not show any long
 tasks in the UI thread anymore.

Review-Url: https://codereview.chromium.org/2567253002
Cr-Commit-Position: refs/heads/master@{#438238}
(cherry picked from commit e3f59ed9bdc15fc1cccc737e425d40a077c36a32)

Committed:
https://chromium.googlesource.com/chromium/src/+/67fac5e016806049e25da6d6e0dd...
==========

[Yusuke Sato, 2016-12-15 16:14:23]

Committed patchset #1 (id:1) manually as
67fac5e016806049e25da6d6e0dd06be69170bb1.